Constant Vigilance
by RebeccaMagic9
Summary: During fourth year, many demigods were in charge of security during the tournament, especially the safety of the champions during classes. Percy Jackson was in charge of Harry's safety, and chaos ensures when he steps foot in the DADA classroom. I do not own Percy Jackson or Harry Potter, they belong to their respective authors. I only came up with the plot line.


_**Disclaimer: See the summary above, but, I'll do this anyway. I do not own Percy Jackson or Harry Potter. They belong to their respective authors, J. K. Rowling and Rick Riordan. I only came up with the plot line.**_

 _ **Harry's P.O.V.**_

Why do I get babysat by an American wizard?

Sure, the other champions are having similar treatment, but, I get the oldest one, and to be honest, the one most likely to be able to kill anyone who ticks him off.

His name is Percy Jackson.

He is eighteen, engaged to be married apparently, well over six feet, extremely muscular (but not body builder muscular), black hair, sea-green eyes, and covered in thousands of scars. He is the type of person who seems nice at first, but then you see someone tick him off and you realise how dangerous he can be.

The other three, Jason Grace, Thalia Grace, and Nico di Angelo, seem similar, yet so different from each other even though they claim to be cousins, Jason and Thalia being siblings. Jason was in charge of keeping an eye on Cedric, Thalia was sticking close to Fleur, and Nico was always around Victor Krum, yet still in the shadows, literally.

I was in DADA when I learnt how dangerous Percy could be and Percy was napping in a chair in the back corner of the room, real helpful that is, when Professor Moody walked in.

He took one look at Percy, shook his head in disgust before starting the lesson. About ten minutes in though, Professor Moody caught us all by surprise by shouting 'CONSTANT VIGILANCE' causing one girl to accidentally fire a hair band in Percy's direction.

A split second after Professor Moody had shouted and the hair tie had been set flying, Percy was wide awake, cut through the hair tie with a knife that appeared from nowhere, and sent two more daggers flying. One hitting the table of the girl whose hair tie it was, almost pinning her hand to the table, and the other rocketing towards Professor Moody, hitting him in the wooden leg and ripping through the wood entirely before embedding itself in the wall behind Professor Moody.

Percy growled at both of them, not sure who to blame for waking him before speaking up.

"If you don't want to find yourself getting hit somewhere more vital for your survival, I suggest that you don't wake me up from my nap," he growled out before standing up and retrieving his daggers, inspecting each ne as he went. When he sat back own, he pulled out a stone of some sort and started grinding it against the dagger that went through the professor's wooden leg.

"Excellent reflexes," Professor Moody praised.

"Why, thank you, professor. I pride myself with my light sleeping. And just a warning to anyone who thinks that the other security that came with me are more relaxed, they are just as paranoid as I am, some even more paranoid than I am," Percy told him.

"I see. Maybe you can explain how to gain constant vigilance to the class?" the DADA professor asked him.

"It isn't something that can really be taught. No, constant vigilance is only be gained through experience. I gained mine the hard way. Constant vigilance is tiring, yes, but once you have it, it has you in its hold for the rest of your life, and even beyond. It protects you, it is your survival instincts keeping you alive. It is your very primal instincts that have no place in civilised society. Once gained, one must learn to balance the instincts with civilised practices, those that cannot have already lost themselves and their constant vigilance is already a waste of sacrifice," Percy preached while snorting.

"But, then again, the same can be said about a shattered or melted core. Our cores hold every drop of our power. A crack in our core causes our magic to go haywire, but very few have ever pushed themselves to the point of shattering or melting their core. Those that have go mad soon after or kill themselves from the unrestrained magic flowing through their veins and arteries. I personally know two people who completely destroyed their cores. One is my cousin, Nico. He pushed himself beyond his limits and his core melted because of the way his body was handling the exertion of magic. Once he recovered, his core remained melted," Percy told us.

"Who was the one with a shattered core?" Hermione asked.

"Me. I tried to control an element I shouldn't have been able to in a dire situation. My anger and other emotions on top of my desire to live shattered my core in the attempt. Ever since, I have to use a lot of magic every day to keep the magic levels at a containable range. It hurts when the core shatters, like a glass ball containing your magic explodes in your chest. The fragments are scattered throughout your body and it hurts like the fields of punishment if you haven't used enough magic. Most of the time, the shards are just a low throb to remind me of my actions, that I will always have to suffer for my survival. My magic just flows in every cell of my existence now, but it isn't something I recommend, shattering your cores, it hurts, and the power you gain is not worth the suffering or the person you could become," Percy told us while looking out the window.

"What do you mean, person you could become?" Ron asked.

"Before I shattered my core, I avoided killing anyone, even someone trying to kill me, at any cost. I had only ever killed monsters that I had no choice to kill and a few humans who got caught up in explosions I set up. The instant my core shattered, the opponent I was facing became my ultimate enemy. I had to destroy her. I attempted to drown her with her own tears and saliva. I was burning her alive with the most deadly and agonising poisons that have ever been created, naturally or unnaturally. I took pleasure in seeing her struggle for breath. I became no better than those I wished to bring justice upon. I became the thing I was born to kill the moment my core shattered, a monster. It took the love of my life begging me to stop, and seeing her fear of me, for me to gain control of myself. Among my family, they say I have more self-control than most of humanity put together, and even then, it took all of my self-control to put a stop to my inner monster. Someone with less control would have succumbed to the monster that their broken core unleashed," Percy told us with a stone cold tone in his voice, and I could tell that he didn't want to be talking about what had happened.

"What inner monster does di Angelo have?" Malfoy sneered.

"That is private information that Nico has not given me permission to share with others. What I can say is that because his core is only melted, it is easier to keep under control and less likely to shatter further," Percy deadpanned with a defensive shield around his voice.

At dinner, Percy was sitting a few seats away from me. He was eating all healthy foods, a huge contrast to what Ron was eating.

Suddenly, an image appeared in front of him.

"PERCY! HE'S BACK! HE'S COME BACK!" a voice screamed from the image. It showed a blonde haired tanned woman in a plain cabin with architecture blueprints on the walls.

"Who is back, Annabeth?" Percy asked, carefully controlled as if it could be a good or bad thing.

"Leo. Leo is alive! He just got here, and you'll never guess who he brought with him," the woman, now identified as Annabeth, answered.

"Let me guess. Calypso, daughter of Atlas, prisoner and sorceress of Ogygia?" Percy asked.

"How did you know that, Percy?" the woman asked.

"If anyone is capable of freeing Lady Calypso, it is Leo. Besides, Leo was completely absorbed with finding a way back to her before his supposed death. Of course he wouldn't come home without her," Percy stated.

"Yes, well, Leo, Calypso and Festus are back and currently getting debriefed by our superiors. Wait, did I just call you during mealtime?" Annabeth stated. Percy nodded wordlessly and the woman blushed.

"I'll call you back when I am next free, Wise Girl. Now, if you would let get back to my dinner, I'm sure that Jason, Nico and Thalia already know, and Jason will most likely be calling Tempest right about now so that he can return to beat some sense into Leo," Percy stated before swiping through the connection.

"What the bloody hell was that?" Ron asked.

"That was family magic that allows us to communicate with each other. As for the lovely Annabeth I was talking to, that was my amazing and beautiful fiancé. As for the sneaky Leo we were talking about, he is a good friend of ours that was presumed dead over a year ago. Turns out that he never died. Poor boy, probably shattered, or at least melted, his core in that fiery explosion and shrapnel. I will have to get an update on that," Percy answered.

"Who is Calypso and Festus?" Hermione asked.

"Calypso is a true sorceress that was imprisoned on a magic island, unable to leave for supporting her immortal father, Atlas, in a war. Festus is a bronze dragon whose master is Leo himself," Percy stated carefully.

"I thought that you said it was hard to shatter or melt your core?" Hermione asked.

"It is difficult as you must do it all in one go or you'll harm yourself more than necessary. Leo practically burnt himself to a crisp before his supposed death. I doubt that his core remained fully intact," Percy spat and everyone's drinks started to levitate out of their cups.

"Mr. Jackson, please control yourself. You are levitating everyone's drinks," Professor Dumbledore stated.

"My apologies," Percy stated and the liquids fell back into their cups.

"Percy, go contract Annabeth. I'll go find my brother and stop him from crossing the ocean to tell off the fire bug," Thalia stated while pushing Percy out of the hall.

We stared at them for a moment before going back to our food.

I saw them lurking around after that right up until the last task, which they appeared in the graveyard during it, each holding a weapon of a different metal. Percy had a bronze sword, Thalia had a silver bow with a silver arrow knocked, Nico had a pure black sword, and Jason had a golden sword.

"You will not go any further," they chanted together at Wormtail, making Cedric and I shiver.

"Who-?" Wormtail tried to ask.

"We are the children of the sea, the sky, and afterlife. We are the defenders of the immortals. We are the saviours of this planet. We are the heroes of Olympus, you will go no further in this foul ritual," they spoke as one.

"I am Lord Voldemort, there is none more powerful than me!" the bundle declared.

"Lies, you are but a mere mortal wizard. You have split your soul, and for that, you shall suffer in the underworld for all eternity," Nico hissed.

"Lies, you are but a mere male, nothing special. You have put the females of this world in danger, taking their innocence in more than one way, for that, the goddess of maidens will hunt you down and use your loins as bait for a werewolf," Thalia growled

"Lies, you are a traitor to your kind, you have placed shame upon your ancestor's noble blood. You have betrayed your bloodline, for that, you shall burn in fire forever more," Jason spat.

"Lies, you have dared to rise against the immortal rulers of Olympus, for that, you will be hung in a cage of stygian iron over the pit of hell until you have rotted a thousand times over," Percy stated in an eerily monotone voice, putting us all more on edge than the other three's declarations. Percy lifted his hand and the wind started to pick up around us, becoming a hurricane with us in the eye of the storm.

"Stop this at once!" the bundle shrieked.

"I, Perseus Zale Jackson, son of the Greek sea god, Poseidon, sentence you to death by order of the Greek and Roman gods. So mote it be," Percy continued. Water started to flow into the eye of the storm as Percy raised his weapon to the sky, lightning started striking the ground as Thalia and Jason raised their weapons to the sky, and the dead rose out of the ground as Nico plunged his sword into the ground.

Within moments, it was done. Wormtail and the bundle had been destroyed. The four 'bodyguards' turned to us and helped us back to the castle.

"What happened?" Professor Dumbledore asked.

"Tom Marvolo Riddle happened. Don't worry, we took care of him and his Death Eaters. He's been taken for his final punishment, one that he won't be escaping for another ten thousand years, dad's been pissed at him for cheating Thanatos," Nico deadpanned.

"Your father?" Professor McGonagall asked.

"Lord Hades, the Greek god of the underworld. Thanatos and my father have been ranting about a wizard who has the gall to evade death, pathetic really," Nico snorted.

"You mean; you are half god?" Hagrid asked.

"The four of us are. I'm a son of Poseidon, the Greek god of the sea. Thalia is the daughter of Zeus and lieutenant of Artemis. Jason is the son of Jupiter. The four of us are four of the most experienced demigods alive," Percy shrugged.

"Shattered and melted cores are more common among demigods. Percy shattered his fighting against the goddess of misery and poisons. Nico did his trying to transport a forty-foot tall ivory statue and two other people as well as himself of Athena from Greece to America using his power over shadows all while defending them from monsters and using his powers over the dead. Then again, for us, fighting for our lives is an everyday thing, we're pretty much bound to shatter or melt our cores at some point due to over exertion," Thalia dismissed easily.

"Yeah, but, well, dad and the rest of the Olympian counsel was getting pissed because of Tom, he was daring to call himself immortal, saying that there was no one in the world more powerful than him, and that kind of stuff. They basically just decided to send us here and deal with it," Nico muttered.

"I see," Professor Dumbledore muttered.

"Yeah, well, we've done our job, so, we're going to head back home and see our real family, man, I miss Annabeth," Percy told us as he waved goodbye, "I also miss my mum's cooking."

"We all miss Aunt Sally's cooking!" the other three yelled at him and with that, they dissolved into mist, leaving behind a simple note.

 _Goodbye, wizarding peoples._

 _In case you didn't realise who we were, this is just a recap. I, Perseus (call me Percy, dammit) Jackson, am the son of the Greek god of the seas, Poseidon. I'm the only demigod since ancient times to have been offered the prize of immortality. I've done a lot of crazy things as a demigod, including jumping into hell to so my daughter-of-Athena girlfriend didn't have to endure it alone, fighting titans, primordials, giants, and gods, holding up the sky, and riding a horse that can run faster than the speed of sound. Nico di Angelo is the son of Hades, otherwise known as the Ghost King for his uncanny control over ghosts. He's a time traveller born during the second world war! He's done some crazy stupid stuff too, but not as much of a stupid scale as me. He's also been turned into a plant, twice! Thalia (don't call me by my mother's maiden name) Grace (dammit, Percy, why did you call me by that name?), is the daughter of Zeus, and the 'right hand woman' of Artemis, basically, she's an eternal maiden and isn't going to age or die until she gets killed in battle. She's done some crazy stuff, but, like Nico, not on the scale of crazy as me. Like Nico, she's been turned into a plant, or should I say, a pine tree? (PERSEUS JACKSON! STOP MAKING PINE TREE PUNS!) Jason Grace, well, he's our Roman representative as a son of Jupiter and Thalia's 'little' brother as he is now technically older than her. He, like me, has done some crazy things, but I still take the cake on crazy things. Jason is the previous praetor of the last surviving Roman legion, and their current Pontifex Maximus (high priest to the gods) whoopee!_

 _So yeah, that's us. Don't bother looking for us. If you ever find yourself in a situation where a wizard or witch decides to claim themselves better than everyone else on the planet, we may just turn up once more. The gods really don't like people stealing their thunderbolts, or tridents, or helms of darkness, or make up kits, or bows and arrows, or, you get the point (Kelp Head, did you seriously make a pun about weapons being having sharp points?)_

 _So, once again, goodbye, and hopefully, we'll never have to meet again._

 _Sincerely, depending on how you look at it,_

 _Percy Jackson._

~time-skip~

The year has been wrapped up, and nobody really remembers the demigods or even talks about them now. It's almost like they never existed…

 _ **End of story**_


End file.
